Mast-cell Tumors

Mast-Cell Tumors in Cats

  • Cancerous (known as “malignant”) round cell tumor; round cell tumors are made up of cells that appear round or oval on microscopic examination; mast-cell tumors are one type of round cell tumor
  • Tumor arising from mast cells
  • “Cutaneous” refers to the skin
  • Mast cells are connective tissue cells that contain very dark granules; the granules contain various chemicals, including histamine; they are involved in immune reactions and inflammation; mast cells can be found in various tissues throughout the body
  • Differentiation is a determination of how much a particular tumor cell looks like a normal cell; the more differentiated, the more like the normal cell
  • Mast-cell tumors of the skin in cats are classified as “compact” (more benign behavior) or “diffuse” (more undifferentiated and aggressive)
  • Mast-cell tumors also may be found in the tissue immediately beneath the skin (that is, the subcutis), spleen, liver, and intestines
  • Mast-cell tumors are the most common tumor found in the spleen of cats
  • Mast-cell tumors can release histamine, leading to the development of hives, reddening of the skin (known as “erythema”), bleeding and bruising, which can be seen around the tumor

Genetics

  • Increased likelihood of developing mast-cell tumors is seen in certain breeds, indicating that a genetic likelihood exists

Signalment/Description of Pet

Species

  • Dogs
  • Cats

Breed Predilections

  • Cats—Siamese

Mean Age and Range

  • Cats—middle-aged, 8–9 years of age for mast-cell tumors affecting the skin (known as “cutaneous mastocytoma”) and older cats for mast-cell tumors found in the intestines or spleen
  • Cats—histiocytic form of mast-cell tumors of the skin (cutaneous mast-cell tumor) occurs in young cats, mean age of 2.4 years

Predominant Sex

  • Cats—male Siamese

Signs/Observed Changes in the Pet

  • Depend on the location and grade of the tumor

Cats

  • Lack of appetite (known as “anorexia”)—most common complaint with mast-cell tumor of the spleen
  • Vomiting and diarrhea—may occur secondary to mast-cell tumors of the spleen or gastrointestinal tract
  • Long-term (chronic) weight loss
  • Sluggishness (lethargy)
  • Mast-cell tumor of the spleen—enlarged spleen (splenomegaly)
  • Intestinal mast-cell tumor—firm, segmental thickenings of the small intestinal wall; spread (metastasis) to the mesenteric lymph nodes, spleen, liver, and (rarely) lungs

Causes

  • Genetic mutation has been identified in up to 30% of mast-cell tumors

Risk Factors

  • Hereditary
  • Certain breeds of dogs and cats are more likely to develop mast-cell tumors (see “Breed Predilections”)

Treatment

Health Care

Cats

  • Surgery—treatment of choice for mast-cell tumors of the skin; only narrow margins around the removed tumor are necessary, as the majority of tumors do not regrow following narrow surgical margin tumor removal
  • Surgical removal of the spleen (known as “splenectomy”)—treatment of choice for mast-cell tumors of the spleen; splenectomy is recommended in cats with large tumor burden in the abdomen, despite spread of the cancer (metastasis)

Activity

  • Limit activity for pets with heavy tumor burden (such as cats with mast-cell tumors of the intestines or spleen)

Medications

  • Medications presented in this section are intended to provide general information about possible treatment. The treatment for a particular condition may evolve as medical advances are made; therefore, the medications should not be considered as all inclusive

Cats

  • Lomustine
  • Vinblastine

Cats

  • Symptomatic treatment—Benadryl; famotidine or other histamine-blocking (H2) agents; omeprazole and sucralfate should be considered for any dog or cat with gross mast-cell disease

Follow-Up Care

Patient Monitoring

  • Evaluate any new masses microscopically
  • Evaluate regional lymph nodes at regular intervals to detect spread (metastasis)
  • Check complete blood count (CBC) at regular intervals, if the pet is receiving chemotherapy
  • Check liver enzymes on serum biochemistry profile, if the pet is on certain chemotherapy drug protocols (such as lomustine therapy)

Cats

  • Abdominal, including mast-cell tumor involving the intestine or spleen—abdominal ultrasound every 3 months for 1 year

Possible Complications

  • Low white blood cell count (known as “leucopenia”) due to suppression of the bone marrow (known as “myelosuppression”) secondary to chemotherapy
  • Liver toxicity (known as “hepatotoxicity”)

Expected Course and Prognosis

  • complete surgical removal (excision) of low-grade mast-cell tumors in most locations is curative
  • Complete surgical removal (excision) of high-grade mast-cell tumors or those located in areas associated with a poor prognosis (mucocutaneous junctions [areas where skin and moist tissues of the body come together; for example, the lips]), possibly inguinal regions) often require chemotherapy; median survival times averages approximately 11–12 months
  • Incomplete surgical removal (excision) of a low-grade mast-cell tumor may require additional local therapy with another surgery (often cured) or radiation therapy (85% disease-free at 3 years)
  • Incomplete surgical removal (excision) of a high-grade mast-cell tumor requires additional local therapy, in addition to chemotherapy; median survival times range from 6 to 12 months
  • Spread of the cancer to lymph nodes in the area of the tumor (regional metastasis) should be treated with surgical removal (excision) of the affected lymph node(s) at the time of the primary tumor removal; chemotherapy is necessary; median survival times are typically less than 9 months
  • Spread of the cancer to lymph nodes located away from the tumor or other organs (known as “distant metastasis”) often is treated with chemotherapy or ancillary therapies alone with a median survival of 4 months or less

Key Points

  • All new masses should be evaluated by a veterinarian
  • Fine-needle aspiration and microscopic examination should be performed as soon as possible on any new mass
  • Surgical removal (excision) should be done as soon as possible on any new mast-cell tumor

Mammary Gland Tumors

Mammary Gland Tumors in Cats (Breast Tumors)

  • Cancerous (malignant) and benign tumors of the breast (mammary glands) in cats
  • “Mammary” refers to a breast or mammary gland
  • The mammary glands produce milk to feed newborn kittens; they are located in two rows that extend from the chest to the inguinal area; the nipples indicate the location of the mammary glands
  • Most cancerous (malignant) breast tumors in cats are carcinomas; benign breast tumors in cats include adenomas, fibroadenomas, and papillomas
  • Spread to the lungs (known as “pulmonary metastasis”) is seen in up to 70% of cats with breast cancer

Genetics

  • The high number of Siamese with breast tumors suggests a genetic component; however, specific genes have not been identified to date

Signalment/Description of Pet

Species

  • Cats; breast (mammary gland) tumors are the third most common type of tumor seen in cats

Breed Predilections

  • Domestic shorthair and longhair cats are affected most commonly, but this likely reflects the popularity of these breeds, rather than a true increased likelihood of developing breast tumors as compared to other cat breeds
  • Siamese have twice the risk of developing breast tumors than other cat breeds

Mean Age and Range

  • Mean—10–12 years of age
  • Range—9 months–23 years of age (although most cats are greater than 5 years of age)
  • Siamese tend to develop breast tumors at a younger age and the incidence begins to plateau around 9 years of age

Predominant Sex

  • Females predominate
  • While being intact (that is, capable of reproducing) increases the risk of breast tumors, most cats diagnosed with breast tumors are spayed females
  • 1–5% of breast cancer (mammary carcinoma) occur in male cats

Signs/Observed Changes in the Pet

  • Masses in the breast tissue; masses may be soft or firm; smaller masses often are freely moveable, whereas larger masses may adhere to the underlying abdominal wall
  • Overlying skin can be intact, but frequently is ulcerated
  • Associated nipple may be inflamed, with discharge of clear fluid
  • Any or all glands may be involved; the caudal two glands (near the rear legs) are affected more commonly than the other glands; left and right sides are affected with equal frequency
  • Approximately 50% of affected pets have multiple gland involvement
  • Infiltrated lymphatic vessels—may appear as subcutaneous (that is, under the skin), linear, beaded chains
  • Cats with advanced metastatic disease may have general signs of illness (such as sluggishness [lethargy], lack of appetite [known as “anorexia”], difficulty breathing [known as “dyspnea”])
  • Cats with inflammatory carcinoma may have severe ulceration; reddening of the skin (known as “erythema”); pain; fluid buildup in the ventral abdomen and pelvic limbs (fluid buildup known as “edema”)

Causes

  • Unknown

Risk Factors

  • Compared to intact female cats (those cats capable of reproducing), cats spayed at less than 6 months of age are 11 times less likely to develop breast cancer (mammary carcinoma) and those spayed between 6 and 12 months of age are 7 times less likely to develop breast cancer
  • Genetic—Siamese
  • Administration of progestins (such as medroxyprogesterone acetate)—increased risk of benign and malignant breast tumor development in female and male cats
  • Number of litters a mother cat (known as a “queen”) has not been shown to affect breast tumor development

Treatment

Health Care

  • Surgery is recommended for cats with tumors confined to the breast tissue, with or without involvement of the nearby lymph nodes (known as “regional lymph-node involvement”)
  • Post-operative chemotherapy is recommended after the cat has recovered from surgery
  • Chemotherapy can be used as the only treatment for cats that have tumors that cannot be removed surgically (so-called “inoperable tumors”), have distant spread of the cancer (metastasis), or both
  • Radiation therapy can be considered to improve local control after surgery or to control inoperable tumors and improve the pet’s condition, but not to cure (known as “palliative treatment”)
  • Palliative treatment is recommended for cats with nonoperable tumors or significant metastasis, or when surgery and chemotherapy are declined

Surgery

  • Radical mastectomy of the affected mammary (breast) chain is recommended; this significantly reduces the risk of local tumor recurrence, as well as recurrence in lymph vessels running through the breast tissueTumors in both mammary chains—perform two radical mastectomies, one on each chain (known as “bilateral radical mastectomies), timed usually 2–4 weeks apart
  • Survival time may be increased with bilateral radical mastectomy; however, some studies suggest that unilateral (that is, one-sided) radical mastectomy may be sufficient to effectively control local disease in some pets
  • In cats with advanced metastatic disease, local mastectomy to control signs and improve the pet’s condition, but not to cure (palliative treatment) can be considered to remove an ulcerated or infected tumor

Medications

  • Medications presented in this section are intended to provide general information about possible treatment. The treatment for a particular condition may evolve as medical advances are made; therefore, the medications should not be considered as all inclusive
  • Chemotherapy—doxorubicin alone or in combination with cyclophosphamideOther chemotherapeutic agents (mitoxantrone, carboplatin, and docetaxel) might have activity
  • Consult with a veterinary oncologist for current chemotherapy recommendations
  • Pain relievers (known as “analgesics”) and antibiotics should be considered for cats with tumors that are painful, ulcerated, or both
  • No available immune response modifier (known as an “immunomodulator,” such as levamisole, bacterial vaccines, and liposomal muramyl peptide) has shown effectiveness
  • Tamoxifen and other selective estrogen receptor modulators have not been evaluated for safety and effectiveness

Follow-Up Care

Patient Monitoring

  • Thorough physical examination—conducted monthly for the first 3 months and then every 2–3 months thereafter; emphasis on checking previous incision line(s), remaining mammary glands, and regional lymph nodes
  • Chest x-rays (radiographs)—three-view radiographs taken every 2 months, to check for spread of the cancer (metastasis) into the lungs

Preventions and Avoidance

  • Spay (ovariohysterectomy)—compared to intact female cats (those cats capable of reproducing), cats spayed at less than 6 months of age are 11 times less likely to develop breast cancer (mammary carcinoma) and those spayed between 6 and 12 months of age are 7 times less likely to develop breast cancer; no obvious protective effect when cats are spayed at greater than 12 months of age

Possible Complications

  • Fluid buildup in the space between the lungs and chest wall (known as “pleural effusion”); life-threatening difficulty breathing (difficulty breathing is known as “dyspnea”)
  • Chemotherapy—reduction of bone-marrow activity (known as “myelosuppression”), resulting in low numbers of red blood cells, white blood cells, and/or platelets; lack of appetite (known as “anorexia”)

Expected Course and Prognosis

  • Most cats die from local recurrence of breast cancer, spread of their cancer (metastasis), or both
  • Tumor size is strongly predictive of prognosis; median survival with tumor diameter greater than 3 cm is 4–6 months after surgery (1–2 months in male cats); median survival with tumor diameter of 2–3 cm, is 1–2 years (5–6 months in male cats); median survival with tumor diameter less than 2 cm is approximately 4.5 years (14 months in male cats)
  • Radical mastectomy significantly reduces the risk for local tumor recurrence; the impact on survival is not as consistent because of the high rate of spread (metastasis) associated with breast cancer in cats
  • For cats with advanced-stage disease treated with chemotherapy alone, response rates are around 50%, with survival times of 6–12 months for cats that have a response to treatment and less than 6 months for cats that do not respond to chemotherapy

Key Points

  • Early detection and aggressive treatment of breast (mammary gland) tumors in cats is very important
  • Many affected pets have advanced disease when first presented for examination by the veterinarian
  • Spay (ovariohysterectomy) at an early age (prior to 6 months) in non-breeding cats has a significant protective effect
  • Given the possible genetic contribution to this disease, particularly in Siamese cats, breeding affected cats is not recommended

Lymphoma

Lymphoma in Cats – Overview

  • Lymphocytes are a type of white blood cell that are formed in lymphatic tissues throughout the body; lymphocytes normally are involved in the immune process
  • Lymphoma is cancer (malignancy) of lymphocytes that usually involves lymph nodes or other lymphatic tissue of the body, but may involve other organs of the body (such as the liver or kidneys)
  • Lymphoma in cats is found in various anatomic locations in the body, including the mediastinum (known as the “mediastinal form of lymphoma”)—the mediastinum is the center portion of the chest that contains the heart and other organs (except for the lungs); the gastrointestinal tract (known as the “alimentary form of lymphoma”); the kidneys (known as the “kidney or renal form of lymphoma”); multiple organs/tissues throughout the body (known as the “multicentric form of lymphoma”); and the spinal cord (known as the “spinal form of lymphoma”)

Signalment/Description of Pet

Species

  • Cats

Breed Predilections

  • Siamese and other Oriental breeds may be more likely to have lymphoma than other cat breeds

Mean Age and Range

  • Mean age of feline leukemia virus (FeLV)-positive cats with lymphoma—3 years
  • Mean age of FeLV-negative cats with lymphoma—7 years
  • Median age of cats with localized lymphoma, outside of the lymph nodes—13 years
  • Most cats with Hodgkin’s-like lymphoma are older than 6 years of age

Signs/Observed Changes in the Pet

  • Depend on anatomic form
  • Mediastinal form (located in the center of the chest)—open-mouthed breathing; coughing; regurgitation; lack of appetite (known as “anorexia”); weight loss; the front part of the chest is very firm and resistant to gentle compression during physical examination
  • Alimentary form (located in the gastrointestinal tract)—lack of appetite (anorexia); weight loss; sluggishness (lethargy); vomiting; constipation; diarrhea; black, tarry stools, due to the presence of digested blood (known as “melena”); frank blood in the stool; thickened intestines or abdominal masses
  • Kidney or renal form—consistent with kidney failure (such as vomiting; lack of appetite [anorexia]; increased thirst [known as “polydipsia”]; increased urination [known as “polyuria”]; and sluggishness [lethargy]); large, irregular kidneys
  • Nasal form (located in the nose or nasal passages)—discharge from the nose (known as “nasal discharge”) or bleeding in the nose and nasal passages (known as “epistaxis” or a “nosebleed”); facial deformity; abnormalities of the eyes; excessive tearing (known as “epiphora”); abnormal breathing sounds; sneezing; lack of appetite (anorexia)
  • Multicentric form (located in multiple organs/tissues throughout the body)—possibly none in early stages; lack of appetite (anorexia), weight loss, and depression with progression of disease; enlargement of lymph nodes throughout the body
  • Spinal form—quickly progressing weakness to partial paralysis in rear legs (known as “posterior paresis”)
  • Cutaneous (skin) lymphoma—itchiness (known as “pruritus); bleeding (hemorrhage); or masses on the skin accompanied by hair loss (hair loss known as “alopecia”)
  • All forms—fever; dehydration; depression; extreme weight loss with muscle wasting (known as “cachexia”) in some pets

Causes

  • Feline leukemia virus infection—pets inconsistently test positive during illness (for example, 85% are positive with the mediastinal form, 45% with the kidney form, 20% with the multicentric form, and 15% with the alimentary (intestinal) forms of lymphoma test positive on FeLV test); older cats with lymphoma are usually FeLV negative, while younger cats are usually FeLV positive

Risk Factors

  • Feline leukemia virus exposure
  • Exposure to environmental tobacco smoke

Treatment

Health Care

  • Outpatient, whenever possible
  • Supportive medical care, if needed depending on clinical signs
  • Fluid therapy, appetite stimulants, and other treatments based on clinical signs
  • Radiation therapy—may be used for localized lymphoma; relapses outside the radiation field are not uncommon
  • Consult a veterinary oncologist for chemotherapy doses, schedules, and to help assess best option(s) for treatment

Activity

  • Normal

Diet

  • No change in most cases; may require dietary change if cat has kidney failure
  • Can add omega-3 (n-3) fatty acids (fish oil origin) to the diet

Surgery

  • To relieve intestinal blockages or obstructions, repair “holes” in the intestinal tract (known as “perforations”) that develop secondarily to the presence of the tumor and to surgically remove individual tumors
  • To obtain biopsy specimens for microscopic examination

Medications

  • Medications presented in this section are intended to provide general information about possible treatment. The treatment for a particular condition may evolve as medical advances are made; therefore, the medications should not be considered as all inclusive
  • Chemotherapy—used in a combination or sequential protocol; some protocols have induction and maintenance periods
  • Many variations of similar combination chemotherapy exist; they all have similar effectiveness
  • Low-grade intestinal lymphoma can respond to oral chlorambucil and prednisone

Follow-Up Care

Patient Monitoring

  • Physical examination, complete blood count (CBC), and platelet count—before each weekly chemotherapy treatment and one week after each time a new drug is administered, of if concerned about low blood cell counts
  • X-rays (radiographs) or advanced imaging—as necessary, depending on location of primary tumor

Preventions and Avoidance

  • Avoid exposure to or breeding feline leukemia virus–positive cats

Possible Complications

  • Low white blood cell counts (known as “leukopenia”)
  • Generalized bacterial infection (sepsis)
  • Lack of appetite (anorexia)

Expected Course and Prognosis

  • Depends on initial response to chemotherapy, anatomic type, feline leukemia virus status, and tumor burden; overall response rate is 50–70% to treatment
  • Median survival with prednisone alone—1.5–2 months
  • Median survival with combination chemotherapy (COP or CHOP)—6–9 months
  • Mediastinal form (located in the center of the chest)—about 10% of affected pets with live more than 2 years
  • Median survival with alimentary form (located in the gastrointestinal tract)—8 months
  • Median survival with peripheral multicentric form (located in multiple organs/tissues: “peripheral” refers to tissues away from the center of the body)—23.5 months
  • Median survival with kidney form—if FeLV-negative, 11.5 months; if FeLV-positive, 6.5 months
  • Median survival with nasal form—1.5–2.5 years with radiation and chemotherapy; chemotherapy may not improve survival over radiation alone
  • Cats with Hodgkin’s-like lymphoma can do well for extended periods of time (months to years), even without treatment

Key Points

  • A treatment protocol should be established that fits the pet and the owner’s lifestyle
  • Side effects of chemotherapy are treatable and should be addressed promptly
  • Goal is to induce remission and achieve a good quality of life for pets for as long as possible
  • More than 80% of pet owners are pleased with their cat’s quality of life during chemotherapy